.\" Copyright (C) 2006 Red Hat, Inc. All Rights Reserved.
.\" Written by David Howells (dhowells@redhat.com)
.\"
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.\" This program is free software; you can redistribute it and/or
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.TH ADD_KEY 2 2016-07-17 Linux "Linux Key Management Calls"
.SH NAME
add_key \- add a key to the kernel's key management facility
.SH SYNOPSIS
.nf
.B #include <keyutils.h>
.sp
.BI "key_serial_t add_key(const char *" type ", const char *" description ,
.BI "                     const void *" payload ", size_t " plen ,
.BI "                     key_serial_t " keyring ");"
.fi
.SH DESCRIPTION
.BR add_key ()
asks the kernel to create or update a key of the given
.I type
and
.IR description ,
instantiate it with the
.I payload
of length
.IR plen ,
and to attach it to the nominated
.I keyring
and to return its serial number.
.P
The key type may reject the data if it's in the wrong format or in some other
way invalid.
.P
If the destination
.I keyring
already contains a key that matches the specified
.IR type " and " description,
then, if the key type supports it, that key will be updated rather than a new
key being created; if not, a new key will be created and it will displace the
link to the extant key from the keyring.
.P
The destination
.I keyring
serial number may be that of a valid keyring to which the caller has write
permission, or it may be a special keyring ID:
.TP
.B KEY_SPEC_THREAD_KEYRING
This specifies the caller's thread-specific keyring.
.TP
.B KEY_SPEC_PROCESS_KEYRING
This specifies the caller's process-specific keyring.
.TP
.B KEY_SPEC_SESSION_KEYRING
This specifies the caller's session-specific keyring.
.TP
.B KEY_SPEC_USER_KEYRING
This specifies the caller's UID-specific keyring.
.TP
.B KEY_SPEC_USER_SESSION_KEYRING
This specifies the caller's UID-session keyring.
.SH KEY TYPES
There are a number of key types available in the core key management code, and
these can be specified to this function:
.TP
.B \*(lquser\*(rq
Keys of the user-defined key type may contain a blob of arbitrary data, and the
.I description
may be any valid string, though it is preferred that the description be
prefixed with a string representing the service to which the key is of interest
and a colon (for instance
.RB \*(lq afs:mykey \*(rq).
.TP
.B \*(lqkeyring\*(rq
Keyrings are special key types that may contain links to sequences of other
keys of any type.
If this interface is used to create a keyring, then a NULL
.I payload
should be specified, and
.I plen
should be zero.
.SH RETURN VALUE
On success
.BR add_key ()
returns the serial number of the key it created or updated.
On error, the value \-1
will be returned and errno will have been set to an appropriate error.
.SH ERRORS
.TP
.B EACCES
The keyring wasn't available for modification by the user.
.TP
.B EINVAL
The payload data was invalid.
.TP
.B EKEYEXPIRED
The keyring has expired.
.TP
.B EKEYREVOKED
The keyring has been revoked.
.TP
.B ENOKEY
The keyring doesn't exist.
.TP
.B ENOMEM
Insufficient memory to create a key.
.TP
.B EDQUOT
The key quota for this user would be exceeded by creating this key or linking
it to the keyring.
.SH LINKING
Although this is a Linux system call, it is not present in
.I libc
but can be found rather in
.IR libkeyutils .
When linking,
.B -lkeyutils
should be specified to the linker.
.SH SEE ALSO
.BR keyctl (1),
.BR keyctl (2),
.BR request_key (2),
.BR keyctl (3),
.BR keyrings (7)
